Semiconductor device and method of manufacturing thereof

Abstract

A plurality of p anode regions are formed at one surface of an n − substrate. A trench is formed in each p anode region. An ohmic junction region is formed between an anode metallic electrode and the p anode region. The p anode region has a minimum impurity concentration at a portion near the ohmic junction region which enables ohmic contact. A cathode metallic electrode is formed at the other surface of the n − substrate with an n + cathode region interposed. Accordingly, a semiconductor device which has an improved withstand voltage and in which the reverse recovery current is reduced can be obtained.

1. A semiconductor device comprising:
 a semiconductor substrate of a first conductivity type; 
 a plurality of trench portions selectively formed at a first main surface of said semiconductor substrate; 
 a conductor embedded in each said trench portion with a first insulating layer there between; 
 a plurality of impurity regions of a second conductivity type which is formed at a region between said trench portions and at said first main surface of said semiconductor substrate, in contact with at least one of opposite sides of adjacent trench portions and located shallower than said trench portion; and 
 a first electrode layer formed on said first main surface of said semiconductor substrate, wherein; 
 said first electrode layer and each said impurity region form an ohmic contact at said first main surface; 
 each said impurity region has a minimum impurity concentration at a portion near said first main surface which enables ohmic contact with said first electrode layer, and has an impurity concentration still lower than said minimum impurity concentration which enables ohmic contact at a portion at said first main surface other than the portion near said first main surface; 
 each said impurity region of the second conductivity type is in contact with at least the edge along the opening of the trench portion and the side, adjacent to the edge, of the trench portion, and each said impurity region of the second conductivity type is in direct contact with the semiconductor substrate of the first conductivity type; and 
 each said impurity region is formed to be in contact with opposite sides of said trench portions adjacent to each other, and said first electrode layer and a region of the first conductivity type of said semiconductor substrate form a Schottky junction at said first main surface. 
 
   
   
     2. The semiconductor device according to  claim 1 , wherein
 said first electrode layer is formed of aluminum, and 
 said minimum impurity concentration which enables ohmic contact with said first electrode layer is 1×10 16 –1×10 17 /cm 3 . 
 
   
   
     3. The semiconductor device according to  claim 1 , wherein
 each said impurity region is formed at both sides of each said trench portion to be in contact with one side of each said trench portion, and 
 said first electrode layer and a region of the first conductivity type of said semiconductor substrate form a Schottky junction at said first main surface. 
 
   
   
     4. The semiconductor device according to  claim 3 , further comprising:
 a second insulating layer formed on each said conductor and electrically insulates said first electrode layer from each said conductor; and 
 an electrode portion electrically connected with each said conductor. 
 
   
   
     5. The semiconductor device according to  claim 3 , wherein
 said first electrode layer is formed of aluminum, and said minimum impurity concentration which enables ohmic contact with said first electrode layer is 1×10 16 –1×10 17 /cm 3 . 
 
   
   
     6. The semiconductor device according to  claim 1 , wherein
 said impurity region is formed to be in contact with opposite sides of said trench portions adjacent to each other, and further comprising: 
 a second insulating layer formed on each said conductor and electrically insulates said first electrode layer from each said conductor; and 
 an electrode portion electrically connected with each said conductor. 
 
   
   
     7. The semiconductor device according to  claim 6 , wherein
 said first electrode layer is formed of aluminum, and said minimum impurity concentration which enables ohmic contact with said first electrode layer is 1×10 16 –1×10 17 /cm 3 . 
 
   
   
     8. The semiconductor device according to  claim 1 , wherein
 said first electrode layer is formed of aluminum, and said minimum impurity concentration which enables ohmic contact with said first electrode layer is 1×10 16 –1×10 17 /cm 3 .